Stacking of planar conjugated rings - beyond aromatics (CROSBI ID 649312)
Prilog sa skupa u zborniku | sažetak izlaganja sa skupa | međunarodna recenzija
Podaci o odgovornosti
Molčanov, Krešimir
engleski
Stacking of planar conjugated rings - beyond aromatics
Stacking of aromatic rings is a well-known type of intermolecular interaction and has found its way into textbooks on supramolecular chemistry. It is usually considered as rather weak (typically <1 kcal mol-1) interaction, having a secondary role in crystal packing. It has been extensively studied and its nature is now well-understood. However, misconceptions about its nature are numerous, and are reflected in a variety of names used, which are often misleading: π∙∙∙π interaction, π-stacking, π-interaction, aromatic interaction, stacking interaction, etc. It is commonly believed that stacking is an exclusive property of aromatic rings, and the fact that other types of planar conjugated rings also stack is overlooked. In fact, the first study of stacking of non-aromatic rings was done by us several years ago. Stacking of planar organic radicals has also been used in design of organic semiconductors and magnetic materials. Our detailed studies have shown that interactions between quinoid rings and semiquinone radicals are by an order of a magnitude stronger than interactions between aromatic rings. As a result of numerous X-ray charge density studies on different types of stacked rings, we propose a generalised model of stacking, which accounts for both aromatic and non-aromatic rings. In the case of closed-shell molecules, the main attractive force is electrostatic, resulting from uneven distribution of electron density - therefore, electrostatic attraction is the strongest in systems with little or no electron delocalisation (such as quinones), while it is weak in systems with fully delolcalised π electrons (i.e. aromatics). In the case of radicals, the dominant interaction is spin coupling, which determines type of stack and interplanar distance ; less-important parameters such as offset and orientation of the stacked rings are a result of electrostatic attraction.
pi-interactions ; charge density ; electrostatic potential ; crystallography
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Podaci o prilogu
25-25.
2017.
objavljeno
Podaci o matičnoj publikaciji
25th Slovenian-Croatian Crystallographic Meeting : Book of Abstracts and Programme
Pevec, Andrej ; Počkaj, Marta
Ljubljana: University of Ljubljana, Faculty of Chemistry and Chemical technology
Podaci o skupu
25th Slovenian – Croatian Crystallographic Meeting
ostalo
14.06.2017-18.06.2017
Ljubljana, Slovenija